Radial beam modulator tube



May 8, 1951 c. c. BATH 2,552,363

RADIAL BEAM MODULATOR TUBE Filed Oct. 28, 1947 E 7 dinan- "-t--ll-l 1i .CARL C. BA'TH MQMUM Patented May 8, 1951 RADIAL BEAM MODULATO-R TUBE CarlY C. Bath, Baltimore, Md., assigner to Bendix Aviation Corporation, Towson, Md., a: corporation of Delaware Application October 28, 1947, Serial No. 782,641

7 Claims.

This invention relates tov vacuum tubes for use in pulse-time modulated communications systems, and more specically it relatesA to a radial beam modulator tube for use. in multi-channel pulse-modulated systems.

In prior art multiplexing systems, conventional vacuum tubes were used. This'resulted in many disadvantages, such as, for-example, the. necessity of using several tubes for each channel utilized, in addition tothe tubesused in the master synchronizing circuits. Each channel also required some means of amplitude limiting to prevent over-modulation, and the consequent cross talk.

Many attempts have been made, in the past few years, to develop a. tube to eliminate these shortcomings of pulse-time modulated multiplex systems. These developments, however, have not solved the problem, and the resultant tubes are bulky, fragile, and costly.

t is an object of this invention to provide a radial beam modulator tube that will be more efdcient than tubes now known to the art.

lt is a further object to provide a tube which functions to permit greater time displacement of the channel pulses without increasing the pos,- sibility of cross talk.

It is a further object to provide az tube that is smaller, more rugged and cheaper to produce than those known to the present art.`

The above objects and advantages have been accomplished by devices embodying the instant invention.

Fig. 1 isa diagrammatic viewl in cross' section illustrating the position of the various elements in a tube embodying the instant invention;

Fig. 2 is a plan View of a tubeofthetype shown in Fig, 1;

Fig. 3 is a cutaway side View of the tube of Fig. 2, taken along the line 2-2 of that iigure.

Fig. 4 is a view of the window plate element in an unrolled positionillustrating the placementof the channel and marker slots, and;

Fig. 5 is a View similar to Fig. 2, illustrating: the position of the two beams and their directiony of rotation together with a' circuit arrangement by which they can be formed.

Referring to the drawing, in particular Figs. l, 2, 3, and. 4, a. radialbeam modulator tube', in accordance with this. invention; is shown. comprising acylindrical cathode element l 0, enclosed by a circular accelerating anode. Il, which is providedwith a centrally located circumferential slot 23. Extendingy outwardly. in aw horizontal plane, but not physically contacting thelowermostportion offthe.accelerating.,anoder|:IV are a plurality. of. deector platesv l2, even in number, but so arranged asV though there were an. odd number, thatv is, each plate is. diametricallyf op posed by a space. The. plates are equally spaced with the-exception that atone point of the circleV a plate is omitted. SurroundingY the deector' plates l2, is a window plate I3, cylindricalin form and incorporating slots, each of which is radially coincident with arespective oneA ofthe plates i2 and isdisposed at an angle with respect to the axis of the cathode I0. Atthepointwhere there is no deflector plate. there is a Widerv slotf25 which extends parallel to the axis ofthe cathode I. Surrounding the Window plate I3is asetof collector plates I4, each located just outside of a respective slot 24S in the window plate I3', all being connectedtov one another electrically:

When the` cathode I0 isl heated by a suitable source, it emits electrons. When a positive voltage is applied to the accelerating anode III, the. electrons emitted from the cathode I0 are attracted thereto. Due to. the'velocity built upaby` the electrons traveling toward the accelerator IVI, some of thesaid electronspass. through the horizontal slot 23 in the accelerator anode in a plane perpendicular to the axis of cathode l0. The result, if no further forces were acting onlthe electron stream', would be.thefformingiofanelectron discfy In operation, howevenasshown in- Fig. 5, the tube is mounted within a. rotating magneticziield generated for example, by tWoLsets of coils l5, I6 and I1, I8: positioned; at; right angles to each other and fed with quadrature currents from a source! 9, by way of a'phase.splitting network comprising a condenser` 2l]` and a resistor 2l The; result isto concentratey the: elec.;- trons4 into two sharply defined beams dia.- metrically opposite each other and rotating around the axis of the cathode lil, as illustrated in Fig. 5, at a uniform rate, which is determined by the frequency of the alternating currents in theY magnetic eld coils. For standard communication systems, the frequency shouldbe; between 4000, and 5000Y cycles per second. The said beamsv pass overv the deflector plates IZQ-before reaching the window plate i3', and d uei tothe odd disposition of thev deflector. plates l2,` only one beam is over a deflector plate at any given time. When one beam has reachedt thetrailing edge of a deiiectorV plate, the opposite beam is about to reach the leadingedge of another de ector plate, as illustrated in Fig, 5, in which the referencenumeral 22 indicates..the-electron beam travelingj the direction indicatedby the-farrows:

SignalI voltages from. several:v communication channels are applied to the deflector plates l2, which tends to raise or depress the beams as they pass over the said plates, depending on the polarity and amplitude of the Voltage on the plate at the time the beam is passing.

The slots 24 in the window plate i3 are out at an angle to the axis of the cathode IG, as illustrated in Fig. 4. if the beam is raised or de- Dressed it will strike the slot at a different time than if it were traveling perpendicular to the axis of cathode it. This is the method used to obtain pulse time modulation. The electrons which pass through the slots 2li in the window plate I3, are collected by the anodes it which are mounted adjacent to each slot. These collector anodes Hl are joined together electrically and connected to an external load circuit, so the electrons passing through the slots in the Window plate i3 cause negative voltage pulses to be present on the collector anode ill. The individual channel pulses are time modulated in ac cordance with the signal voltages applied to the individual deilecting plate l2. IThe wide slot 25 in the window plate i3, positioned in the space which has no defiecting plate, generates a wide unmodulated pulse for synchronization purposes.

If a signal, too large in amplitude, is applied to a deiiector plate l2, the beam will be driven beyond the end of the slot in window plate it, and the pulse will be momentarily removed. This will cause peak clipping of the modulating signal, but it cannot result in cross-tall.- or spillover into adjacent channels, and due to this, the instant invention is self limiting.

It is quite feasible to add another accelerating anode concentric with the accelerating anode ll, to obtain a still sharper focusing of the beam.

While the drawings illustrate the present invention with 8 deflector plates and a window plate with a corresponding number of Windows,

it is to be understood that there can be employed any even number desired up to aboot 2li. The marker slot in the window plate can be other than one wide slot as illustrated in the drawings, for example, two narrow slots parallel to each other can be used, so long as an unmodulated pulse can pass.

Furthermore, the collector anodes, by the use f suitable material, understood by those skilled in the art, can be used as secondary emitters,

thus, using the window plate as the collector.

What is claimed is: l. A radial beam modulator tube comprising; a cylindrical cathode; an accelerating a circumferential planar slot; a plurality of deilector plates positioned in a common plane oliset from the plane of said slot and extending normally to the axis of said cathode, said ,deflector plates being mounted in a circle about said anode and being equally spaced with each plate diametrically opposed by a space between a pair oi said plates, said circle of plates-being interrupted by the omission of a plate therefrom; a cylindrical element surrounding said circle or" plates and coaxial with said cathode, said element being provided with a plurality of slots, said slots extending at a uniform angle with respect to the axis of said` element and each of said slots being located in symmetrical radial coincidence with a respective one of said plates, said element being provided with a slot extending parallel to the axis thereof and located in radial coincidence with said interruption in said Circle of plates, and a plurality of collector plates,

anode Surrounding said cathode and being formed with each located outside of said element and in radial coincidence with a respective one of said slots, said collector plates being connected together electrically.

2. A radial beam modulator` tube as claimed in claim l, including means adjacent said tube for producing a magnetic field within said tube.

3. A radial beam modulator tube comprising a cathode, means adjacent said tube for forming the electrode stream from said cathode into a beam extending diametrically of said tube and rotatable about said cathode, va plurality of spaced deilector plates disposed -with their major surfaces in parallelism with the path of said beam, each of said plates being diametrically opposite a space between adjacent plates so that a plane deiined by said beam and extending normal to said plates will intersect only one of said plates at a time as said beam rotates, and anode means disposed in radial coincidence with each of said plates for intercepting said electron stream.

4. A radial beam modulator tube comprising a cathode, means adjacent said tube for forming the electrode stream from said cathode into a beam extending diametrically of said tube and rotatable about said cathode, means adjacent the path of said beam for sequentially applying deiiecting forces to alternate ends of said beam as it rotates, a plurality of spaced anode elements for said beam, each of said anode elements being positioned in said path to intercept said beam during the application of one of said deecting forces thereto, and means between said cathode and said anode elements for Varying the time at which interception of said beam by each of said anode means occurs, said variation being a function of the defiecting forces applied lwhile said beam and said anode means are radially fcoincident.

5. A radial beam modulator tube comprising a cathode, means adjacent said tube for forming the electron stream from said cathode into a beam extending dametrically of said tube and rotatable about said cathode, a plurality of spaced deflector plates disposed with their major surfaces in parallelism with the path of said beam, each of said plates being diametrically opposite a space between adjacent plates so that a plane dened by said beam and extending normal to said plates will intersect only one of said plates `at e, time as said beam rotates, anode means disposed in radial coincidence with each oi said plates for intercept ing said electron stream, and apertured masking means located between said cathode and said anode means.

6. A radial beam modulator tube comprising a cathode, means adjacent said tube for forming the electrode stream from said cathode into a beam extending diametrically of said tube and rotatable about said cathode, means adjacent the path of said beam for sequentially deflecting alternate ends of said beam in lateral directions from its path of rotation, a plurality of anode means positioned in the path of said beam to intercept said beam during each of said lateral delections, and an apertured masking means located between said cathode and said anode means, each of the apertures 0f said masking means being located between said cathode and a respective one of said anode means and shaped to vary the time of interception of said beam by said respective one of said anode means as a function of the lateral deflection of said beam from said path. Y

7. A radial beam modulator tube comprising a cathode, means for forming an electron stream into a beam extending diametrically of said tube and rotatable about its central portion, deflecting means adjacent the path of said beam for sequentially modulating alternate ends of said 5 beam by causing lateral deviation thereof from the normal path of rotation, means inthe path of said beam for intercepting the modulated portion of the beam during each of said deviations and means between said cathode and said intercepting means for varying the time of said interception in terms of the degree and direction of said lateral deviation.

CARL C. BATH.

6 REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,164,922 Hellmann July 4, 1939 2,217,774 `Skellett O-ct. 15, 1940 2,320,756 `Skellett June 1, 1943 2,391,967 Hecht et al Jan. 1, 1946 2,433,403 Skellett Dec. 30, 1947 2,461,250 Bailey Feb. 8, 1949 2,465,827 A'aler Mar. 29, 1949 

